The East Bay hills are dotted with hundreds of ponds, many of which offer welcome habitat and shelter to native wildlife, from threatened California red-legged frogs and tiger salamanders to toxic newts, voracious water bugs, and migrating waterfowl. Just about any pond, from a verdant clear blue pool to the merest muddy puddle, has something interesting going on beneath the surface. But perhaps the most remarkable fact about these ponds is that nearly all of them were created as watering holes for livestock. Today, the East Bay Regional Park District is working to understand the complex relationships between native species, grazing cattle, and artificial ponds.